Flywheels are energy storage devices competitive with electrochemical batteries. Their advantage is greatly increased when they are suspended magnetically without physical contact with machinery housing, as is typical with rolling element or fluid film bearings. Magnetic suspension greatly decreases power losses due to bearing drag torque in comparison with rolling element or fluid film bearings. Many applications of flywheels require compact size and low weight, while maintaining a high level of stored energy. One difficulty experienced with employing magnetic suspension with flywheels, as well as many other applications, is the instability of a control system when confronted with a member or shaft that rotates at high speeds.
In addition to the particular application of flywheels, there is a need for stable magnetic suspension systems in many applications utilizing high speed rotating shafts or other members. For example, momentum wheels are an important and effective means of controlling the attitude of orbital satellites. Similar problems are also experienced with turbo compressors for air conditioning units utilized on aircraft and in other high performance vehicles. Turbomolecular vacuum pumps are another example of an application that would benefit from a stable magnetic suspension system for high speed rotating shafts. Many other applications may also benefit from the development of a stable magnetic suspension system that may be used to control rotating machinery for industrial and military applications. The instability of such magnetic suspension systems for high speed applications inherently limit such development.